The bulk of the collection are two series of correspondence. One series contains letters written to him by his wife Margaret "Maggie" Mitchell Caine, his father John T. Caine, and his friends. The other series are letters written to his wife Maggie. Other than these letters the collection has a few items from their son Free Caine. This material primarily come from items he sent and received while on an L.D.S. mission to Japan.